(25) Real-World Utilization and Patient Characteristics of Biologic vs. Biosimilar Rituximab from a Specialty Pharmacy

Background: : Rituximab has been available as Rituxan®, the originator biologic, since 1997. Its biosimilars, Truxima® (2018) and Ruxience® (2019), were launched to help mitigate rising healthcare costs and improve patient access.
Currently, limited studies exist comparing populations using originator rituximab versus its biosimilars.

Objective: : This study aims to assess rituximab user characteristics and utilization patterns to better understand the factors influencing biosimilar uptake, and to support payers in developing effective biosimilar implementation strategies.

Methods: : This retrospective observational study utilized dispensing data from California Specialty Pharmacy between January 1, 2020 and March 31, 2025. Patients were included if they had at least one fill for Rituxan®, Ruxience®, or Truxima®, and excluded if they switched rituximab products during the study period. Eligible patients were grouped based on their first rituximab product dispensed. Collected variables included age, gender, insurance type, and primary ICD-10 codes. Diagnoses were categorized into clinical classifications: autoimmune, oncology, etc. Proportional matching was conducted based on the overall cohort’s interquartile age range and gender ratio. A Chi-square test was conducted to assess whether there was a significant difference in indication (autoimmune vs. oncology) across rituximab products. Utilization trends were graphed by monthly dispensing volume.

Results: : The study cohort’s (15% Rituxan®, 37% Ruxience®, and 48% Truxima® users) distribution of therapeutic areas varied between originator and biosimilar users. Rituxan® users were predominantly treated for autoimmune indications (48%), whereas oncology indications were more common among Ruxience® (65%) and Truxima® (64%) users. This trend persisted after matching. The Chi-square test yielded a p-value of 0.0008. Utilization trends showed early Truxima® uptake, followed by increased Ruxience® uptake, with both biosimilars showing comparable utilization in the recent year.

Conclusions: : This study found statistically significant association between rituximab product and indication. These findings suggest therapeutic setting or payer-related factors may influence product selection and warrant further investigation.

Sponsorship:: California Specialty Pharmacy